The four EBS optimized instance types are m3.xlarge, m3.2xlarge, m2.2xlarge and c1.xlarge for dedicated bandwidth or throughput between the EC2 instances and EBS volumes. The performance or bandwidth ranges from 500 Mbits (500 / 8 = 62.5 MBytes) per second, to 1,000 Mbits (1,000 / 8 = 125MBytes) per second depending on the type of instance. As a refresher, EC2 instances (why by time you read this could change) vary in size and functionality with different amounts of EC2 Unit of Compute (ECU), number of virtual cores, amount of storage space included, 32 or 64 bit, storage and networking IO performance, and EBS Optimized or not. In addition to instances, different operating system images can be installed using those licensed from AWS such as various Windows and Unix or supply your own.

There are also different generations of instances such as M1 (first generation where one ECU = 1.0 to 1.2 Ghz of a 2007 era Opteron or Xeon processor), M3 (second generation with faster processors) along with Micro low-cost options. There are also other optimized instances including high or large amounts of memory, high CPU or compute processing, clustered compute, high memory clustered, clustered GPU (e.g. using Nivida Tesla GPUs), high IO and high storage space capacity needs.

Here is the announcement from AWS:

Dear Amazon Web Services Customer,

We are delighted to announce the global availability of EBS-optimized support for four additional instance types: m3.xlarge, m3.2xlarge, m2.2xlarge, and c1.xlarge. EBS-optimized instances deliver dedicated throughput between Amazon EC2 and Amazon EBS, with options between 500 Megabits per second and 1,000 Megabits per second depending on the instance type used. The dedicated throughput minimizes contention between EBS I/O and other traffic from your Amazon EC2 instance, providing the best performance for your EBS volumes.

EBS-optimized instances are designed for use with both Standard and Provisioned IOPS EBS volumes. Standard volumes deliver 100 IOPS on average with a best effort ability to burst to hundreds of IOPS, making them well-suited for workloads with moderate and bursty I/O needs. When attached to an EBS-optimized instance, Provisioned IOPS volumes are designed to consistently deliver up to 2000 IOPS from a single volume, making them ideal for I/O intensive workloads such as databases. You can attach multiple Amazon EBS volumes to a single instance and stripe your data across them for increased I/O and throughput performance.

What this means is that AWS is enabling customers to size their compute instances and storage volumes with more flexibility to meet different needs. For example, EC2 instances with various compute processing capabilities, amount of memory, network and storage I/O performance to volumes. In addition, storage volumes based on different space capacity size, standard or provisioned IOP’s, bandwidth or throughput performance between the instance and volume, along with data protection such as snapshots.

This means that the cost per space capacity of an EBS volume varies based on which AWS availability zone it is in, standard (lower IOP performance) or provisioned IOP’s (faster), along with instance type. In other words, cloud storage is not just about the cost per GByte, it’s also about the cost for IOPS, bandwidth to use it, where it is located (e.g. with AWS which Availability Zone), type of service, level of availability and durability among other attributes.